With reference to FIGS. 1, 2, and 3, a perspective view, an assembled cross sectional view in compressing air and after compressing air of a prior art oil can are illustrated. The prior art oil can includes a body 1, a tube 12, a seat 13, a trumpet seat 14, a small stopper 15, a larger stopper 16, a piston seat 2, a telescopic tube 25, a jetting head 26, a lock head 27. The cylindrical body 1 has an outer thread 11 at the protrusion of the upper opening. In order that the compressed air, filling air and oil can be jet out, an U shape piston seat 2 is disposed at the upper side of the body 1. A via hole 22 for receiving the telescopic tube 25 is installed atop the piston seat 2. The lateral side of the via hole is installed with a vent 23. In order that the that the aftersaid piston hat can be engaged and slides for compressing air, a concave chamber 24 is installed at the periphery of the piston seat 2. In order that the piston seat 2 can be tightly combined with the body 1 at the upper side, a pad 21 is installed therebetween. In order to control the flowing of high pressure air, a large stopper 16, a small stopper 15, and a trumpet seat 14 with via hole 141 are sequentially installed within the piston seat 2 (i. e. below the via hole 22 and vent 23). An engaging seat 13 with a via hole 132 at the center thereof and a wind portion at the lateral side 131 are installed below the trumpet seat 14. A tube 12 is installed below the engaging seat 13 with a via hole 132 at the center thereof and a wind portion at the lateral side 131. The telescopic tube 25 with a vent 252 at the center thereof is installed with a block 252 for be engaged with the jet head 26 of the jet hole 261. In order that the piston seat 2 can be fixed to the outer thread 11 atop the body 1, a lock head 27 with an inner thread 271 can be installed at the outer cover. A piston hat 28 with a block 282 having a long tube 281 is installed at the inner periphery of the U shape piston seat 2.
With reference to FIG. 2, when a high pressure air is desired to be compressed into the body 1, a long tube 281 having a block 282 below the piston hat 28 is passed through the concave seat 24 and then is pulled rapidly. As it is pushed downwards, the air 3 above the long tube 281 of the piston hat 28 will flow into the piston seat 2 through the air hole 23 to enter into the piston seat 2. The air will push away the large stopper 16 and then flows through the small stopper 15, and then flow into the body 1 with oil 31 from the via hole 141 of a trumpet seat 14 (as indicated by arrow). As the piston hat 28 is pulled upwards, air 3 will enter into the long tube 281 for pressing downwards next time.
With reference to FIG. 3, as air is compressed into the body 1, high pressure air 3 will push the large and small stoppers 15 and 16 installed between the piston seat 2 and the trumpet seat 14 upwards, the large stopper 16 will seal the air hole 23 atop the piston seat 2. Thus, high pressure air 3 can not flow out from the via hole 141 of the trumpet seat 14. Therefore, high pressure air 3 is sealed to fill fully in the body 1.
With reference to FIG. 4, a prior art device for jetting air and oil is illustrated by an assembled cross sectional view. As the oil is desired to be jetted out, the jetting head 26 must be pressed down, then the telescopic tube 25 is pressed down synchronously. Thus tube 25 with a seal lower side and a via hole 252 will enter into the piston seat 2, and then the large and small stopper 15 and 16 will press down, so that the high pressure air 3 will flow into the via hole 141 of the trumpet seat 26 to be jetted out. Then, the tube 12 at the center of the trumpet seat 14 and the seat 13 will be released with the high pressure air 3 so as to carry out the oil 31 within the body 1.
However, prior art structure has some defects. For example, each time in using, the piston hat 28 must be covered for compressing high pressure air 3 and then moves longitudinally. With the increment of the air pressure within the body 1, it becomes more and more difficult with a large power. When the oil can is used, the piston hat 28 must be pulled out to be further stored, otherwise, the jetting head 26 can not be pressed down. Moreover, the prior art piston hat 26 has not any confining structure, thus, as it is pulled out, a large traveling length will be induced so that the hat 26 falls out. Therefore, prior art structure is not a convenient design.